I wonder if you can test the speaker's performance by bridging the connections from the L&R rear speakers...that should essentially double the input wattage? EE's correct me if I'm wrong, but it works in my head...

would it be possible to use the ba amp output as an input for another amp ?

Since apparently I'm the only one who is responding to this post, I guess I'll continue. Yes, you can use the output from the stock BA amp as an input to another amp. Keep in mind though, that if your second amp doesn't have a built in crossover adjustment, you'll definitely only want to tap the output for the front door speakers, as the stock BA amp has a build in crossover and the "woofer" in the door is only receiving low frequency sound right now.

Essentially, you could take the amplified output from the BA amp to the front speaker by cutting the existing wire and then splice back into that existing wire (which is wired to the front speaker) for the new amp's output.

Tricky, but might work. You'll probably require a 2-channel amp to do that, unless you can wire both the front woofers to the same terminal on the new amp (not sure how that would work).

Also, d@mn it's nice to know the Hemi WK's can reach to the kind of mileage you have right now!